Photographic processing of exposed silver halide films comprise several steps. The simplest process, used for black and white films, involves, development, fixing, washing, and an optional stop bath. Processes used in processing conventional color films involve development, bleaching, fixing (or combined bleach-fix) and a stabilizer-wash.
In the E-6 reversal process, including variations thereof, photographic reversal film is exposed to a black and white developer, followed by a wash, a reversal bath containing stannous ion, color development, a pre-bleach, bleaching, an optional wash, fixing, and a final wash or rinse. In commercial operations developers are used continuously to develop multiple rolls of photographic films. Moreover environmental regulations are promoting recycling and regeneration of color developers. In these circumstances concentrations of tin can increase. Concentrations greater than about 200 mg/L can have undesirable sensitometric effects on photographic film being developed. At much higher concentrations the stannate form of tin can also produce undesirable effects.
Methods for the removal of tin from seasoned photographic color developers are needed. Moreover, methods of the removal of tin from reversal bath overflows are similarly needed. Seasoned photographic color developers, according to the present specification, are those developers that could adversely affect the sensitometry of films because of the relatively high concentration of tin therein.